Residential and commercial irrigation systems for turf and landscaping typically include one or more solenoid operated valves that are turned ON and OFF by an electronic irrigation controller. The valves admit water to various branch lines in the form of subterranean pipes that each supply several sprinklers connected at spaced intervals. Each combination of a solenoid valve and its associated sprinklers is referred to in the irrigation industry as a zone or station. A modern electronic irrigation controller typically includes a microprocessor that executes one or more stored watering programs. These watering programs are typically programmed or selected by the user via push button and/or rotary knob. The controller usually has a liquid crystal display (LCD) to facilitate programming by the user. The microprocessor controls the solenoid valves via suitable drivers and switching devices. The valves are opened and closed by the microprocessor in accordance with the programmed run and cycle times for each of the stations.
Modular expandable irrigation controllers have gained increasing popularity in both residential and commercial landscape applications. In a modular irrigation controller, the base portion of the irrigation controller contains the microprocessor and user actuated manual controls. Each station is then controlled by a corresponding station module which comprises a plastic housing that supports a station module circuit, as well as wire connection terminals for connecting wires that lead to a plurality of solenoid actuated irrigation valves. Typically each station module can independently control more than one solenoid actuated valve. The station modules contain pins, sockets, card edge connectors or some other standard form of electro-mechanical connectors for allowing them to be connected and disconnected from the base portion of the irrigation controller. The station modules are typically inserted into receptacles in either the housing that contains the microprocessor or a separate back panel connected to the microprocessor housing. A station module is typically connected to each solenoid actuated valve by a dedicated field valve line, for example, twelve gauge wire. A common return line is connected between all of the valves and the irrigation controller. Triacs in the station module circuit are typically used to switch a twenty-four volt AC power signal ON and OFF relative to each of the field valve lines.
The principal advantage of a modular expandable irrigation controller is that the base portion of the controller need only be equipped with the minimum number of station modules that can control the total number of stations required to irrigate the turf and/or landscaping of a particular system installation. Thus, for example, an irrigation system may have only three zones, requiring only a single station module, while another may have twelve zones which might require four station modules. Considerable cost savings are thus achieved and the distributor need not stock a wide size range of irrigation controllers. Moreover, if an irrigation system expands after initial installation because the landscaping has increased, additional station modules can be added. Furthermore, if a station module is damaged by a lightening strike, or otherwise fails, it can be replaced.
One drawback of conventional modular irrigation controllers is that the user typically connects the field vale lines to the station modules when the AC power to the modules is “live,” presenting a risk of electric shock. If an indoor mounted controller is first disconnected from the AC wall outlet, there is a risk that the watering programs stored in the controller will be lost. Outdoor mounted controllers are usually hard-wired to an AC power source. To reduce the risk of electric shock, the user must first locate and turn off a circuit breaker, typically at a remote and inconvenient location, before connecting or re-connecting field valve line wires. Again, there is a risk of losing the watering programs when the power is shut off to the irrigation controller in this fashion.
Yet another problem with conventional modular controllers is that replacement of a damaged or defective station module requires disconnection and re-connection of the field valve lines to the station module. This is tedious, and often leads to mis-connection of the field valve lines when more than one station module is replaced at the same time.